The present invention relates to a double twist spindle apparatus which is arranged to wind yarns after two lines of first-twisted component yarns are drawn and arranged together, and second twisting operation is performed.
As yarn twisting machines for the manufacture of synthetic fiber for industrial use such as tire cord, there are disclosed well-known double twist spindle apparatuses in U.S. Pat. No. 4,063,408 and Japanese Published Unexamined Patent Application No.42931/1982. An example of conventional double twist spindle apparatus is fundamentally illustrated in FIG. 8.
In the FIG. 8, reference numeral 71 represents a hollow spindle rotatably supported by a bolster 72. The hollow spindle 71 is provided with a yarn inserting hole 74 and a rotating disc 75. The rotation of a spindle driving motor 73 is transmitted to the hollow spindle 71 through pulley 76, belt 77 and pulley 78, while the rotation of the hollow spindle 71 is transmitted to a first pulley 82 which is provided with a permanent magnet 81 through pulley 79 and belt 80.
Reference numeral 83 represents a stationary member supported by the hollow spindle 71 and is kept under non-rotating state. On a bobbin supporting shaft 84 of the stationary member 83, a bobbin holder 85 is rotatably supported. On the bobbin holder 85, a take-up bobbin 86 is fitted and fixed. The bobbin holder 85 is provided with pulleys 87 and 88.
The stationary member 83 has a pulley supporting shaft 89 on which the first pulley 82 is rotatably supported and a second pulley 91 provided with a magnetic plate 90 is also rotatably and movably supported in the axial direction. The permanent magnet 81 and the magnetic plate 90 stand face to face each other with gap S therebetween. Since the magnetic plate 90 is attracted by the permanent magnet 81, when the first pulley 82 is rotated, the second pulley 91 also rotates. When the gap S is small, the driving force to be transmitted from the first pulley 82 to the second pulley 91 is large, while when the gap S is large, the driving force becomes small. The rotation of the second pulley 91 is transmitted to the bobbin holder 85 through a belt 92 and the pulley 87, whereby the take-up bobbin 86 is rotated.
The stationary member 83 is provided with a cam supporting shaft 93 on which a traverse cam shaft 94 is rotatably supported. When the traverse cam shaft 94 is rotated, a traverse guide 95 performs straight reciprocating motion. The rotation of the bobbin holder 85 is transmitted to the traverse cam shaft 94 through the pulley 88, a belt 96 and a pulley 97.
Two lines of the first-twisted component yarns Y are guided into the hole 74 of the hollow spindle 71 and wound around the take-up bobbin 86 guided by the rotating disc 75, traverse guide 95 and the like as shown in the FIG. 8. At this stage, the two lines of yarns Y are arranged together and second twisting operation is performed with the rotation of the hollow spindle 71.
As the lines of yarns Y are wound around the take-up bobbin 86, winding diameter of the take-up bobbin 86 is increased. For instance, when the number of revolutions of the take-up bobbin 86 is constant, winding speed of the lines of yarns Y is increased as the winding diameter increases. It is inconvenient that the winding speed changes. Arrangement is, therefore, made to change the number of revolutions of the second pulley 91 relative to the number of revolutions of the first pulley 81 as previously described. It is also desired to regulate the number of revolutions of the second pulley 91 so as to make the winding speed constant.
The double twist spindle apparatus shown in the FIG. 8 is provided with a sensor 98 for detecting winding diameter of the take-up bobbin 86 and a gap regulating means 99 for changing the gap S by changing the position of the second pulley 91 in the axial direction corresponding to the winding diameter. By regulating the gap S, magnetic attracting force between the permanent magnet 81 and the magnetic plate 90 is regulated, and transmission torque which is transmitted from the first pulley 82 to the second pulley 91 can be regulated. Consequently, it becomes theoretically possible for the take-up bobbin 86 to wind the lines of yarns Y with a constant winding speed under a constant tension.
However, there are the following two problems in the prior art described above. The first problem will now be described.
In order to wind the lines of yarns Y around the take-up bobbin 86 with a constant speed, it is required to decrease the number of revolutions of the take-up bobbin 86 as winding diameter increases and it necessitates to decrease the transmission of driving torque by enlarging the gap S. On the other hand, since the self-weight of the take-up bobbin 86 is increased as winding diameter increases, it is required to increase the transmission of the driving torque in order to wind the lines of yarns Y with a constant tension by rotating the take-up bobbin 86 whose self-weight is increased, and it eventually necessitates to reduce the gap S.
As described above, it is required to enlarge the gap S for keeping winding speed constant as winding diameter of the take-up bobbin 86 increases, while it is required to reduce the gap S for keeping winding tension constant. It is very difficult to regulate the gap S in order to satisfy the above described requirements which are contrary to each other. Moreover, since the magnetic transmission torque between the first pulley 82 and the second pulley 91 changes in quadric relative to the change of the gap S, it becomes more difficult to regulate the gap S.
In the prior art, it is difficult to keep the winding speed and the winding tension of the take-up bobbin 86 constant since the regulation of the gap S can not be made well. Practically, in the conventional apparatus, the winding tension is increased as the winding diameter increases, and it causes to break the lines of yarns Y or produces irregularity in twisting.
The second problem is as follows. As shown in the FIG. 8, the conventional apparatus is arranged to rotate the hollow spindle 71 and the bobbin holder 85 by a single driving source (spindle driving motor 73). Accordingly, it is impracticable to freely and readily change the rotational velocity ratio between the hollow spindle 71 and the bobbin holder 85. Consequently, there remains a problem that changes in the number of twist, winding speed, winding tension and the like can not be performed simply.